1. Field of the Invention
This invention relates generally to a trip strip that provides a turbulated air flow within cooling channels in a blade of a gas turbine engine and, more particularly, to a trip strip that provides a turbulated air flow within cooling channels in a blade of gas turbine engine, where the trip strip has a saw tooth configuration.
2. Discussion of the Related Art
The world's energy needs continue to rise which provides a demand for reliable, affordable, efficient and environmentally-compatible power generation. A gas turbine engine is one known machine that provides efficient power, and often has application for an electric generator in a power plant, or engines in an aircraft or a ship. A typically gas turbine engine includes a compressor section, a combustion section and a turbine section. The compressor section provides a compressed air flow to the combustion section where the air is mixed with a fuel gas, such as propane. The combustion section includes a plurality of circumferentially disposed combustors each including an injector that injects the fuel gas into the combustor to be mixed with the air and an igniter that ignites the fuel/air mixture using an electrical discharge to generate a working gas typically having a temperature greater than 1300° C. The working gas expands through the turbine section and is directed across rows of blades therein by associated vanes. As the working gas passes through the turbine section, it causes the blades to rotate, which in turn causes a shaft to rotate, thereby providing mechanical work
The temperature of the working gas is tightly controlled so that it does not exceed some predetermined temperature for a particular turbine engine design because to high of a temperature can damage various parts and components in the turbine section of the engine. However, it is desirable to allow the temperature of the working gas to be as high as possible because the higher the temperature of the working gas, the faster the flow of the gas, which results in a more efficient operation of the engine.
In certain gas engine turbine designs, a portion of the compressed air flow is also used to provide cooling for certain components in the turbine section, typically the vanes, blades and ring segments. The more cooling and/or the more efficient cooling that can be provided to these components allows the components to be maintained at a lower temperature, and thus the higher the temperature of the working gas can be. For example, by reducing the temperature of the compressed gas, less compressed gas is required to maintain the part at the desired temperature, resulting in a higher working gas temperature and a greater power and efficiency from the engine. Further, by using less cooling air at one location in the turbine section, more cooling air can be used at another location in the turbine section. In one known turbine engine design, 80% of the compressed air flow is mixed with the fuel to provide the working gas and 20% of the compressed air flow is used to cool the turbine section parts. If less of that cooling air is used at one particular location as a result of the cooling air being lower in temperature, then more cooling air can be used at other areas in the turbine section for increased cooling.
It is known in the art to provide a serpentine cooling air flow channel within the blades in the turbine section, where the air flows up one channel and down an adjacent channel in a back and forth motion before the cooling air exits the blade. In one known cooling air flow channel design, a series of specially configured turbulators or trip strips are positioned within the flow channels that cause the airflow over the trip strips to become turbulated and create an air vortex. The disturbance in the air flow provided by the trip strip augments the local heat transfer coefficient of the air and thus enhances the cooling performance. Improvements can be made to the trip strips to further enhance the cooling performance.